#include <iostream>
#include <fstream>

int main()
{
    std::ifstream in("fractii.in");
    std::ofstream out("fractii.out");

    unsigned long int N;
    in >> N;
    unsigned long int nr = 2*N - 1;

    for(int i = 2; i < N; ++i){
        for(int j = i + 1; j <= N; ++j){
            if(j % i != 0){
                nr += 2;
            }
        }
    }

    out << nr;
    return 0;
}